Increasing use of sheets of waterproof membrane, usually made of a plastic or rubber material, has created problems in attaching these sheets of membrane material to the upper surface of the roof. One method employed is to glue the entire sheet to the roof or to the insulation which has been previously placed on the roof. The cost of doing this adds considerable expense to the construction. Another method that is employed is mechanically to fasten blocks or disk to the roof and then glue the sheet to the mechanically fastened blocks or disk. Again, this can result in weak points involving leaks and is an expensive procedure. Another approach is merely to attach the sheets to the periphery of the roof and lay ballast consisting of small stones on the roof. In large span industrial applications this creates a structural problem since the ballast weighs one-half ton per 100 square feet and also the ballast is reflective so that there are no solar heat advantages possible.
If there were no wind, the membrane could merely be laid on the roof, perhaps sealed around the edges, and no problems would arise. However, when the wind blows over the roof, it will cause the membrane to rise up because of the negative pressure created above the roof by the wind blowing and also as a result of the effect of vortexes formed from other buildings in the area and, as a result, frontal pressure and wind drag can stretch or dislodge the membrane causing failure and leaks in the roof.
One approach to solve this problem is shown in U.S. Pat. No. 4,223,486, Kelly, which provides a plurality of one-way or duckbilled valves which are connected between the membrane and the support on which the membrane is placed so that when a negative pressure is created above the membrane, the presence of the exhaust valve will tend to equalize the pressure, and thus prevent uplift of the loosely-laid membrane. While this system has merit, all it does is equalize the pressure above and below the membrane but does not create any positive force to hold the membrane down and in position against the roof surface as the wind velocity increases.